This paper is a report on a study of shrinkage-weight loss relationships for normal and high stre... more This paper is a report on a study of shrinkage-weight loss relationships for normal and high strength concrete specimens of different sizes. The maximum aggregate size used in concrete mixes was 10mm. Three geometrically similar test specimens of a cylindrical shape with diameters of 37.5 mm, 75 mm and 150 mm and a height/diameter ratio of two were used in the experiments. All specimens were subjected to standard air drying in a temperature and humidity controlled laboratory (average relative humidity 50±6% and temperature 17±1 0 C) for a period of 60-70 days. Weight loss and shrinkage measurements were conducted on the specimens prepared with normal and high strength concrete. Results indicated that the time required for the same weight loss ratio was found to be about 7.4 and 8.5 times longer for the largest specimen size than the smallest specimen for normal and high strength concrete respectively.
Sigma Journal of Engineering and Natural Sciences, 2007
Normal dayanımlı betondan hazırlanan çift konsol elemanlara, konsol eksenlerine paralel basınç yü... more Normal dayanımlı betondan hazırlanan çift konsol elemanlara, konsol eksenlerine paralel basınç yüklemesi uygulanmıştır. Yüklemeler iki farklı mesnetlenme durumu için uygulanarak birbirleriyle karşılaştırılmıştır. Numune kalınlıkları sabit olup t=40 mm' dir. Diğer boyutlar, büyük ...
Bu çalışmada, Türkiye'nin ilk dengeli konsol yöntemi ile yapılmış Kömürhan Köprüsü'nün düşey yükl... more Bu çalışmada, Türkiye'nin ilk dengeli konsol yöntemi ile yapılmış Kömürhan Köprüsü'nün düşey yükler altında yerdeğiştirmeleri, gerilme dağılımları hesaplanmıştır. Bu amaçla ANSYS programında, malzeme özellikleri ve sınır koşulları dikkate alınarak köprünün gerçek durumunu yansıtan sonlu eleman modeli oluşturulmuştur. Kömürhan Köprüsü, ana açıklığı 143.5m olan simetrik, kenar mesnetleri karada, öngerilmeli kutu kesitli köprüdür. Köprüde yapılan kamyon yüklemesi altında ölçülen yerdeğiştirme, sonlu elemanlar ile modellenen yapıda elde edilen yerdeğiştirme birbirine çok yakın bulunmuştur. Gerçek davranışı veren modelde aşırı yükler altında köprüde çekinceli kesitlerde yerdeğiştirmeler, normal gerilmeler, kesme gerilmeleri elde edilmiştir. Köprüdeki aşırı yerdeğiştirmelerin, normal, kesme gerilmelerinin çekinceli kesitlerde elde edilmesi köprü güvenliği için önemlidir.
Journal of Materials in Civil Engineering, Sep 1, 2009
Concrete structures have traditionally been designed on the basis of strength criteria. This impl... more Concrete structures have traditionally been designed on the basis of strength criteria. This implies that geometrically similar structures of different sizes should fail at the same nominal stress. However, this is not quite true in many cases because of the Size Effect, which may be understood as the dependence of the concrete structure on its characteristic dimension. The actual concrete strength of relatively larger structural members may be significantly lower than that of the standard size. By neglecting the Size Effect, predicted load capacity values become increasingly less conservative as a member size increases. Also, very large structures such as dams, bridges, and foundations are too large and too strong to be tested at full scale in the l aboratory. In recent years, major advances have been made in understanding of scaling and Size Effect. However, these advances remain only in the static domain (i.e., slow loading rates), and none of the previous studies have addressed the effect of higher loading rates or high-strength concrete (HSC) on the Size Effect. Structural concrete can be subjected to high loading rates, such as those associated with impact and explosion incidents. Such load conditions are generated by dropped objects, vehicle collision into structures, accidental industrial explosions, missile impacts, military explosions, etc. The Size Effect in normal strength concrete (NSC) is a phenomenon explained by a combination of plasticity and fracture mechanics, and it is related to the energy balance during the damage/fracture process which causes a change in the mode of failure of the concrete member with the increase in its size, thus causing a reduction in its strength. Although structural response and damage evolution are expected to be size-dependent, it is not clear how time or the material strength affect this phenomenon. In this study, the Size Effect phenomenon was investigated under iv compressive static and impact loads for both normal and high-strength concrete cylinders. This study was conducted by performing 127 compressive static and impact tests on both normal and high-strength concrete and 192 numerical simulations. The tests provided data whose analysis produced evidence on the effect of loading rate and material strength on the Size Effect for structural concrete in compression. Parallel pre-and post-test computational simulations were used to perform 'numerical tests' of the same specimens, and to explore the role of the time dimension on the physical phenomena that contribute to the Size Effect. Comparisons between test and numerical data assisted and guided the investigators in identifying the governing parameters that define the physical phenomena. In addition, the precision test data assisted in validating the computational tools used for the study. This thesis describes this multinational collaborative study (with experimental tests performed at three different locations: Penn State University, USA; the National Defense Academy, Japan; and the University of British Colombia, Canada), and it presents data from both the unique impact tests and the related numerical simulations. Two material models were developed to simulate the dynamic Size Effect that was proved to exist in this study. The study also proved the existence of Size Effect in parameters other than strength such as the modulus of elasticity and the strain at maximum stress. This necessitated modifying the existing Size Effect which was mainly confined to the strength parameter only. Use of high-speed photography enabled the detection of several modes of failure experienced by concrete cylinders subjected to axial impact. v TABLE OF CONTENTS LIST OF FIGURES .
Test results from a Type I & II size effect experimental study on notched and un-notched beams ar... more Test results from a Type I & II size effect experimental study on notched and un-notched beams are presented in this paper. The test specimens were geometrically similar but had different scale ratios and different notch length ratios of 0, 0.02, 0.075, 0.15 and 0.3. The specimens had rectangular cross sections with constant thickness of 40 mm and the depth varied from 40 mm to 500 mm corresponding to a scale ratio of 1:12.5. Rotations measured at support locations for each specimen are presented to reinforce the experimental findings. It was observed that all specimens with different notch-to-length ratios exhibited size effect, in which the stress at maximum load (failure load divided by crosssectional area) decreased as the size was increased. The results indicate that the failure is governed by fracture mechanics principles. This phenomenon is not addressed in current design codes, which do not account for such size effect. The test results showed that beams with shallow notch exhibit Type I, beams with deep notch exhibit Type II size effect law. The test results compared favorably with several widely accepted size effect models.
This study investigates the size effect in concrete by indirect tension tests such as the "splitt... more This study investigates the size effect in concrete by indirect tension tests such as the "splitting test" and "4-point loading test". Size effect is observed in the strength of concrete specimens with different sizes. Cylinder and prism shaped specimens were tested for investigating size effect. Dimensions of the cylinders were 150x300, 75x150, 37.5x75mm, the prisms were 100x100x500, 50x50x250, 25x25x125mm. The cylinders were tested in a loading press (UTC-4730 3000) with 3000kN capacity, the prisms were tested in a MTS loading frame (C45.305) using 50kN load cell. All tests were performed under load control, which the test setup was programmed to reach the max. load in 3 minutes. Type II size effect formula for notched specimens proposed by Bazant were used for analysis of the experimental results.
Double cantilever beams elements which have been prepared from normal strength concrete are appli... more Double cantilever beams elements which have been prepared from normal strength concrete are applied compressive loads as parallel to cantilever axes. Loading are applied to two different supporting conditions and compared with each other. Specimen's thickness' t are constant and 40 mm. Other sizes are geometrically similar with ratio from large specimens to little specimens 4:2:1. Two horizontal and one vertical displacements are measured for each specimens and opening displacements are found for adding to horizontal displacements for each cantilever ends. Energy absorbed capacities are determined by utilizing from each specimen area of under the load-opening displacement curve. Test results arranged for size effect curve and size effect parameters are obtained. Experiments simulated with ANSYS 5.4 finite element programs and fracture toughness' are found with helping this program.
Gümüşhane üniversitesi fen bilimleri enstitüsü dergisi, Nov 17, 2020
kontrollü bir şekilde yıkılana kadar 86 yıl boyunca hizmet veren tarihi Fil Köprüsü'nün yapısal v... more kontrollü bir şekilde yıkılana kadar 86 yıl boyunca hizmet veren tarihi Fil Köprüsü'nün yapısal ve dinamik özellikleri incelenmiş ve kayıt altına alınmaya çalışılmıştır. Bu amaçla, yerinde alınan ölçümlerle, köprünün rölevesi çıkarılmış, hasarsız test metotları kullanılarak malzeme özellikleri belirlenmiştir. Elde edilen bilgiler ışığında köprü, SAP2000 programı kullanılarak modellenmiş, dinamik özellikleri (titreşim periyotları ve mod şekilleri) hesaplanmıştır. Bilgisayar modeli yardımıyla bulunan bu sonuçlar, yapı üzerinde alınan serbest titreşim ölçümlerinden hesaplanan titreşim periyotlarıyla da karşılaştırılmıştır.
Journal of King Saud University: Engineering Sciences, 1994
Results of an initial series of four-day creep tests of mortar specimens under constant shear and... more Results of an initial series of four-day creep tests of mortar specimens under constant shear and cycled humidity conditions of 100% to '50 % and back, are reported. The tests are conducted in a triaxial torsional testing machine. Tested cylinders are sufficiently small to achieve uniform moisture content in short time, sealed, loaded by torque. Significant differences in creep at different humidity conditions are observed. The results are helpful for the formulation of constitutive relations.
Geometrik olarak benzer farkli boyutlu yapilarin, kirilma anindaki nominal gerilme degerlerinin e... more Geometrik olarak benzer farkli boyutlu yapilarin, kirilma anindaki nominal gerilme degerlerinin elemaninkarakteristik boyutu ile azalmasi boyut etkisi olarak tanimlanmaktadir. Betonarme elemanlarin gocme yukundeboyut etkisinin sadece betonun cekme gerilmelerini tasiyamadigi icin degil basinc gerilmelerini tasiyamadigi icinolusan kirilmalarda da gecerli oldugu arastirmalarla gorulmustur. Ayni durum ongerilmeli betonlar, betonarmekolonlar icin de gecerlidir. Bu calismada dort nokta yuklemesi altinda denge ustu donatili dikdortgen betonarmekirislerde gevrek gocme yuklerine karsilik gelen boyut etkisi analizleri yapilmis ve sonuclar Bazant’in boyut etkisiyasalari kullanilarak degerlendirilmistir. Gevrek numunelerde artik gerilmeler kaydedilmis ve Matlab® dahazirlanan kisa bir programla, Marquardt-Levenberg algoritmasi kullanilarak Bazant’in boyut etkisi ifadesindemodellenmistir. Kullanilan iki metod birbirleriyle kiyaslanmistir. Bu calisma boyut etkisinin onemini acikcaortaya koymaktadi...
Abstract The size effect has been investigated and fracture energy, GF, determined for a range of... more Abstract The size effect has been investigated and fracture energy, GF, determined for a range of different strength concretes. The test specimen geometry used in the study was a compact compression prism. Five sizes of geometrically similar specimens with increasing ...
Test results obtained as part of a size-effect study on axially loaded plain concrete columns are... more Test results obtained as part of a size-effect study on axially loaded plain concrete columns are presented. The test specimens were geometrically similar concrete columns (with dimensions in the ratio 1:2:4) having slenderness ratios of 9·7, 18·0 and 34·7. The columns were of square cross-section with sides of 50, 100 and 200 mm and varied in length from 145 mm to 2080 mm. Although such columns are at the bottom end of practical column sizes, the test results extend existing research information on size effects in columns. It was observed that for all slenderness ratios, the failure loads exhibited a size effect. The nominal stress at maximum load (maximum load divided by nominal cross-sectional area) decreased as the size of the columns increased. This behaviour is not taken into account in current design codes and needs further investigation to include practical column sizes. The results are not inconsistent with the 'size-effect law' proposed by Bazant.
The results of full-scale failure of singly reinforced four-point-bend beams of different sizes c... more The results of full-scale failure of singly reinforced four-point-bend beams of different sizes containing deformed longitudinal reinforcing bars are reported. The tests consisted of four groups with one, two and three different size combinations. The specimens were made of concrete with a maximum aggregate size of 10 mm. The beams were geometrically similar in one, two and three-dimensions, and even the bar diameter and cover thicknesses were scaled in proportion. The reinforcement ratio was 3%. The results revealed the existence of a significant size effect, which can approximately be described by the size effect law previously proposed by Bazant. The size effect is found to be stronger in two-dimensional similarities than for one and three-dimensional similarities.
♠Corresponding author, e-mail: [email protected] ... Drying Effect of Normal and High Strength C... more ♠Corresponding author, e-mail: [email protected] ... Drying Effect of Normal and High Strength Concrete ... Sıddık ŞENER 1♠ , Hikmet Duygu ŞENER 2 , Varol KOÇ 3 ... 1 Gazi University, Faculty of Engineering and Architecture, Department of Civil Engineering, 06570 Ankara, ...
Concrete structures have traditionally been designed on the basis of strength criteria. This impl... more Concrete structures have traditionally been designed on the basis of strength criteria. This implies that geometrically similar structures of different sizes should fail at the same nominal stress. However, this is not quite true in many cases because of the Size Effect, which may be understood as the dependence of the concrete structure on its characteristic dimension. The actual concrete strength of relatively larger structural members may be significantly lower than that of the standard size. By neglecting the Size Effect, predicted load capacity values become increasingly less conservative as a member size increases. Also, very large structures such as dams, bridges, and foundations are too large and too strong to be tested at full scale in the l aboratory. In recent years, major advances have been made in understanding of scaling and Size Effect. However, these advances remain only in the static domain (i.e., slow loading rates), and none of the previous studies have addressed the effect of higher loading rates or high-strength concrete (HSC) on the Size Effect. Structural concrete can be subjected to high loading rates, such as those associated with impact and explosion incidents. Such load conditions are generated by dropped objects, vehicle collision into structures, accidental industrial explosions, missile impacts, military explosions, etc. The Size Effect in normal strength concrete (NSC) is a phenomenon explained by a combination of plasticity and fracture mechanics, and it is related to the energy balance during the damage/fracture process which causes a change in the mode of failure of the concrete member with the increase in its size, thus causing a reduction in its strength. Although structural response and damage evolution are expected to be size-dependent, it is not clear how time or the material strength affect this phenomenon. In this study, the Size Effect phenomenon was investigated under iv compressive static and impact loads for both normal and high-strength concrete cylinders. This study was conducted by performing 127 compressive static and impact tests on both normal and high-strength concrete and 192 numerical simulations. The tests provided data whose analysis produced evidence on the effect of loading rate and material strength on the Size Effect for structural concrete in compression. Parallel pre-and post-test computational simulations were used to perform 'numerical tests' of the same specimens, and to explore the role of the time dimension on the physical phenomena that contribute to the Size Effect. Comparisons between test and numerical data assisted and guided the investigators in identifying the governing parameters that define the physical phenomena. In addition, the precision test data assisted in validating the computational tools used for the study. This thesis describes this multinational collaborative study (with experimental tests performed at three different locations: Penn State University, USA; the National Defense Academy, Japan; and the University of British Colombia, Canada), and it presents data from both the unique impact tests and the related numerical simulations. Two material models were developed to simulate the dynamic Size Effect that was proved to exist in this study. The study also proved the existence of Size Effect in parameters other than strength such as the modulus of elasticity and the strain at maximum stress. This necessitated modifying the existing Size Effect which was mainly confined to the strength parameter only. Use of high-speed photography enabled the detection of several modes of failure experienced by concrete cylinders subjected to axial impact. v TABLE OF CONTENTS LIST OF FIGURES .
International Journal of Solids and Structures, 2018
The Double Cantilever Beam (DCB) Mode I fracture testing has been widely used in fracture testing... more The Double Cantilever Beam (DCB) Mode I fracture testing has been widely used in fracture testing of especially fiber reinforced polymer composites and adhesive joints. Application of classical DCB testing to plain concrete or
The universal size effect law of concrete is a law that describes the dependence of nominal stren... more The universal size effect law of concrete is a law that describes the dependence of nominal strength of specimens or structure on both its size and the crack (or notch) length, over the entire of interest, and exhibits the correct small and large size asymptotic properties as required. The main difficulty has been the transition of crack length from 0, in which case the size effect mode is Type 1, to deep cracks (or notches), in which case the size effect mode is Type 2 and fundamentally different from Type 1. The current study is based on recently obtained comprehensive fracture test data from three-point bending beams tested under identical conditions. In this test, the experimental program consisted of 80 three-point bend beams with 4 different depths 40, 93, 215 and 500mm, corresponding to a size range of 1:12.5. Five different relative notch lengths, a/D = 0, 0.02, 0.075, 0.15, 0.30 were cut into the beams. A total of 20 different geometries (family of beams) were tested. The p...
This paper is a report on a study of shrinkage-weight loss relationships for normal and high stre... more This paper is a report on a study of shrinkage-weight loss relationships for normal and high strength concrete specimens of different sizes. The maximum aggregate size used in concrete mixes was 10mm. Three geometrically similar test specimens of a cylindrical shape with diameters of 37.5 mm, 75 mm and 150 mm and a height/diameter ratio of two were used in the experiments. All specimens were subjected to standard air drying in a temperature and humidity controlled laboratory (average relative humidity 50±6% and temperature 17±1 0 C) for a period of 60-70 days. Weight loss and shrinkage measurements were conducted on the specimens prepared with normal and high strength concrete. Results indicated that the time required for the same weight loss ratio was found to be about 7.4 and 8.5 times longer for the largest specimen size than the smallest specimen for normal and high strength concrete respectively.
Sigma Journal of Engineering and Natural Sciences, 2007
Normal dayanımlı betondan hazırlanan çift konsol elemanlara, konsol eksenlerine paralel basınç yü... more Normal dayanımlı betondan hazırlanan çift konsol elemanlara, konsol eksenlerine paralel basınç yüklemesi uygulanmıştır. Yüklemeler iki farklı mesnetlenme durumu için uygulanarak birbirleriyle karşılaştırılmıştır. Numune kalınlıkları sabit olup t=40 mm' dir. Diğer boyutlar, büyük ...
Bu çalışmada, Türkiye'nin ilk dengeli konsol yöntemi ile yapılmış Kömürhan Köprüsü'nün düşey yükl... more Bu çalışmada, Türkiye'nin ilk dengeli konsol yöntemi ile yapılmış Kömürhan Köprüsü'nün düşey yükler altında yerdeğiştirmeleri, gerilme dağılımları hesaplanmıştır. Bu amaçla ANSYS programında, malzeme özellikleri ve sınır koşulları dikkate alınarak köprünün gerçek durumunu yansıtan sonlu eleman modeli oluşturulmuştur. Kömürhan Köprüsü, ana açıklığı 143.5m olan simetrik, kenar mesnetleri karada, öngerilmeli kutu kesitli köprüdür. Köprüde yapılan kamyon yüklemesi altında ölçülen yerdeğiştirme, sonlu elemanlar ile modellenen yapıda elde edilen yerdeğiştirme birbirine çok yakın bulunmuştur. Gerçek davranışı veren modelde aşırı yükler altında köprüde çekinceli kesitlerde yerdeğiştirmeler, normal gerilmeler, kesme gerilmeleri elde edilmiştir. Köprüdeki aşırı yerdeğiştirmelerin, normal, kesme gerilmelerinin çekinceli kesitlerde elde edilmesi köprü güvenliği için önemlidir.
Journal of Materials in Civil Engineering, Sep 1, 2009
Concrete structures have traditionally been designed on the basis of strength criteria. This impl... more Concrete structures have traditionally been designed on the basis of strength criteria. This implies that geometrically similar structures of different sizes should fail at the same nominal stress. However, this is not quite true in many cases because of the Size Effect, which may be understood as the dependence of the concrete structure on its characteristic dimension. The actual concrete strength of relatively larger structural members may be significantly lower than that of the standard size. By neglecting the Size Effect, predicted load capacity values become increasingly less conservative as a member size increases. Also, very large structures such as dams, bridges, and foundations are too large and too strong to be tested at full scale in the l aboratory. In recent years, major advances have been made in understanding of scaling and Size Effect. However, these advances remain only in the static domain (i.e., slow loading rates), and none of the previous studies have addressed the effect of higher loading rates or high-strength concrete (HSC) on the Size Effect. Structural concrete can be subjected to high loading rates, such as those associated with impact and explosion incidents. Such load conditions are generated by dropped objects, vehicle collision into structures, accidental industrial explosions, missile impacts, military explosions, etc. The Size Effect in normal strength concrete (NSC) is a phenomenon explained by a combination of plasticity and fracture mechanics, and it is related to the energy balance during the damage/fracture process which causes a change in the mode of failure of the concrete member with the increase in its size, thus causing a reduction in its strength. Although structural response and damage evolution are expected to be size-dependent, it is not clear how time or the material strength affect this phenomenon. In this study, the Size Effect phenomenon was investigated under iv compressive static and impact loads for both normal and high-strength concrete cylinders. This study was conducted by performing 127 compressive static and impact tests on both normal and high-strength concrete and 192 numerical simulations. The tests provided data whose analysis produced evidence on the effect of loading rate and material strength on the Size Effect for structural concrete in compression. Parallel pre-and post-test computational simulations were used to perform 'numerical tests' of the same specimens, and to explore the role of the time dimension on the physical phenomena that contribute to the Size Effect. Comparisons between test and numerical data assisted and guided the investigators in identifying the governing parameters that define the physical phenomena. In addition, the precision test data assisted in validating the computational tools used for the study. This thesis describes this multinational collaborative study (with experimental tests performed at three different locations: Penn State University, USA; the National Defense Academy, Japan; and the University of British Colombia, Canada), and it presents data from both the unique impact tests and the related numerical simulations. Two material models were developed to simulate the dynamic Size Effect that was proved to exist in this study. The study also proved the existence of Size Effect in parameters other than strength such as the modulus of elasticity and the strain at maximum stress. This necessitated modifying the existing Size Effect which was mainly confined to the strength parameter only. Use of high-speed photography enabled the detection of several modes of failure experienced by concrete cylinders subjected to axial impact. v TABLE OF CONTENTS LIST OF FIGURES .
Test results from a Type I & II size effect experimental study on notched and un-notched beams ar... more Test results from a Type I & II size effect experimental study on notched and un-notched beams are presented in this paper. The test specimens were geometrically similar but had different scale ratios and different notch length ratios of 0, 0.02, 0.075, 0.15 and 0.3. The specimens had rectangular cross sections with constant thickness of 40 mm and the depth varied from 40 mm to 500 mm corresponding to a scale ratio of 1:12.5. Rotations measured at support locations for each specimen are presented to reinforce the experimental findings. It was observed that all specimens with different notch-to-length ratios exhibited size effect, in which the stress at maximum load (failure load divided by crosssectional area) decreased as the size was increased. The results indicate that the failure is governed by fracture mechanics principles. This phenomenon is not addressed in current design codes, which do not account for such size effect. The test results showed that beams with shallow notch exhibit Type I, beams with deep notch exhibit Type II size effect law. The test results compared favorably with several widely accepted size effect models.
This study investigates the size effect in concrete by indirect tension tests such as the "splitt... more This study investigates the size effect in concrete by indirect tension tests such as the "splitting test" and "4-point loading test". Size effect is observed in the strength of concrete specimens with different sizes. Cylinder and prism shaped specimens were tested for investigating size effect. Dimensions of the cylinders were 150x300, 75x150, 37.5x75mm, the prisms were 100x100x500, 50x50x250, 25x25x125mm. The cylinders were tested in a loading press (UTC-4730 3000) with 3000kN capacity, the prisms were tested in a MTS loading frame (C45.305) using 50kN load cell. All tests were performed under load control, which the test setup was programmed to reach the max. load in 3 minutes. Type II size effect formula for notched specimens proposed by Bazant were used for analysis of the experimental results.
Double cantilever beams elements which have been prepared from normal strength concrete are appli... more Double cantilever beams elements which have been prepared from normal strength concrete are applied compressive loads as parallel to cantilever axes. Loading are applied to two different supporting conditions and compared with each other. Specimen's thickness' t are constant and 40 mm. Other sizes are geometrically similar with ratio from large specimens to little specimens 4:2:1. Two horizontal and one vertical displacements are measured for each specimens and opening displacements are found for adding to horizontal displacements for each cantilever ends. Energy absorbed capacities are determined by utilizing from each specimen area of under the load-opening displacement curve. Test results arranged for size effect curve and size effect parameters are obtained. Experiments simulated with ANSYS 5.4 finite element programs and fracture toughness' are found with helping this program.
Gümüşhane üniversitesi fen bilimleri enstitüsü dergisi, Nov 17, 2020
kontrollü bir şekilde yıkılana kadar 86 yıl boyunca hizmet veren tarihi Fil Köprüsü'nün yapısal v... more kontrollü bir şekilde yıkılana kadar 86 yıl boyunca hizmet veren tarihi Fil Köprüsü'nün yapısal ve dinamik özellikleri incelenmiş ve kayıt altına alınmaya çalışılmıştır. Bu amaçla, yerinde alınan ölçümlerle, köprünün rölevesi çıkarılmış, hasarsız test metotları kullanılarak malzeme özellikleri belirlenmiştir. Elde edilen bilgiler ışığında köprü, SAP2000 programı kullanılarak modellenmiş, dinamik özellikleri (titreşim periyotları ve mod şekilleri) hesaplanmıştır. Bilgisayar modeli yardımıyla bulunan bu sonuçlar, yapı üzerinde alınan serbest titreşim ölçümlerinden hesaplanan titreşim periyotlarıyla da karşılaştırılmıştır.
Journal of King Saud University: Engineering Sciences, 1994
Results of an initial series of four-day creep tests of mortar specimens under constant shear and... more Results of an initial series of four-day creep tests of mortar specimens under constant shear and cycled humidity conditions of 100% to '50 % and back, are reported. The tests are conducted in a triaxial torsional testing machine. Tested cylinders are sufficiently small to achieve uniform moisture content in short time, sealed, loaded by torque. Significant differences in creep at different humidity conditions are observed. The results are helpful for the formulation of constitutive relations.
Geometrik olarak benzer farkli boyutlu yapilarin, kirilma anindaki nominal gerilme degerlerinin e... more Geometrik olarak benzer farkli boyutlu yapilarin, kirilma anindaki nominal gerilme degerlerinin elemaninkarakteristik boyutu ile azalmasi boyut etkisi olarak tanimlanmaktadir. Betonarme elemanlarin gocme yukundeboyut etkisinin sadece betonun cekme gerilmelerini tasiyamadigi icin degil basinc gerilmelerini tasiyamadigi icinolusan kirilmalarda da gecerli oldugu arastirmalarla gorulmustur. Ayni durum ongerilmeli betonlar, betonarmekolonlar icin de gecerlidir. Bu calismada dort nokta yuklemesi altinda denge ustu donatili dikdortgen betonarmekirislerde gevrek gocme yuklerine karsilik gelen boyut etkisi analizleri yapilmis ve sonuclar Bazant’in boyut etkisiyasalari kullanilarak degerlendirilmistir. Gevrek numunelerde artik gerilmeler kaydedilmis ve Matlab® dahazirlanan kisa bir programla, Marquardt-Levenberg algoritmasi kullanilarak Bazant’in boyut etkisi ifadesindemodellenmistir. Kullanilan iki metod birbirleriyle kiyaslanmistir. Bu calisma boyut etkisinin onemini acikcaortaya koymaktadi...
Abstract The size effect has been investigated and fracture energy, GF, determined for a range of... more Abstract The size effect has been investigated and fracture energy, GF, determined for a range of different strength concretes. The test specimen geometry used in the study was a compact compression prism. Five sizes of geometrically similar specimens with increasing ...
Test results obtained as part of a size-effect study on axially loaded plain concrete columns are... more Test results obtained as part of a size-effect study on axially loaded plain concrete columns are presented. The test specimens were geometrically similar concrete columns (with dimensions in the ratio 1:2:4) having slenderness ratios of 9·7, 18·0 and 34·7. The columns were of square cross-section with sides of 50, 100 and 200 mm and varied in length from 145 mm to 2080 mm. Although such columns are at the bottom end of practical column sizes, the test results extend existing research information on size effects in columns. It was observed that for all slenderness ratios, the failure loads exhibited a size effect. The nominal stress at maximum load (maximum load divided by nominal cross-sectional area) decreased as the size of the columns increased. This behaviour is not taken into account in current design codes and needs further investigation to include practical column sizes. The results are not inconsistent with the 'size-effect law' proposed by Bazant.
The results of full-scale failure of singly reinforced four-point-bend beams of different sizes c... more The results of full-scale failure of singly reinforced four-point-bend beams of different sizes containing deformed longitudinal reinforcing bars are reported. The tests consisted of four groups with one, two and three different size combinations. The specimens were made of concrete with a maximum aggregate size of 10 mm. The beams were geometrically similar in one, two and three-dimensions, and even the bar diameter and cover thicknesses were scaled in proportion. The reinforcement ratio was 3%. The results revealed the existence of a significant size effect, which can approximately be described by the size effect law previously proposed by Bazant. The size effect is found to be stronger in two-dimensional similarities than for one and three-dimensional similarities.
♠Corresponding author, e-mail: [email protected] ... Drying Effect of Normal and High Strength C... more ♠Corresponding author, e-mail: [email protected] ... Drying Effect of Normal and High Strength Concrete ... Sıddık ŞENER 1♠ , Hikmet Duygu ŞENER 2 , Varol KOÇ 3 ... 1 Gazi University, Faculty of Engineering and Architecture, Department of Civil Engineering, 06570 Ankara, ...
Concrete structures have traditionally been designed on the basis of strength criteria. This impl... more Concrete structures have traditionally been designed on the basis of strength criteria. This implies that geometrically similar structures of different sizes should fail at the same nominal stress. However, this is not quite true in many cases because of the Size Effect, which may be understood as the dependence of the concrete structure on its characteristic dimension. The actual concrete strength of relatively larger structural members may be significantly lower than that of the standard size. By neglecting the Size Effect, predicted load capacity values become increasingly less conservative as a member size increases. Also, very large structures such as dams, bridges, and foundations are too large and too strong to be tested at full scale in the l aboratory. In recent years, major advances have been made in understanding of scaling and Size Effect. However, these advances remain only in the static domain (i.e., slow loading rates), and none of the previous studies have addressed the effect of higher loading rates or high-strength concrete (HSC) on the Size Effect. Structural concrete can be subjected to high loading rates, such as those associated with impact and explosion incidents. Such load conditions are generated by dropped objects, vehicle collision into structures, accidental industrial explosions, missile impacts, military explosions, etc. The Size Effect in normal strength concrete (NSC) is a phenomenon explained by a combination of plasticity and fracture mechanics, and it is related to the energy balance during the damage/fracture process which causes a change in the mode of failure of the concrete member with the increase in its size, thus causing a reduction in its strength. Although structural response and damage evolution are expected to be size-dependent, it is not clear how time or the material strength affect this phenomenon. In this study, the Size Effect phenomenon was investigated under iv compressive static and impact loads for both normal and high-strength concrete cylinders. This study was conducted by performing 127 compressive static and impact tests on both normal and high-strength concrete and 192 numerical simulations. The tests provided data whose analysis produced evidence on the effect of loading rate and material strength on the Size Effect for structural concrete in compression. Parallel pre-and post-test computational simulations were used to perform 'numerical tests' of the same specimens, and to explore the role of the time dimension on the physical phenomena that contribute to the Size Effect. Comparisons between test and numerical data assisted and guided the investigators in identifying the governing parameters that define the physical phenomena. In addition, the precision test data assisted in validating the computational tools used for the study. This thesis describes this multinational collaborative study (with experimental tests performed at three different locations: Penn State University, USA; the National Defense Academy, Japan; and the University of British Colombia, Canada), and it presents data from both the unique impact tests and the related numerical simulations. Two material models were developed to simulate the dynamic Size Effect that was proved to exist in this study. The study also proved the existence of Size Effect in parameters other than strength such as the modulus of elasticity and the strain at maximum stress. This necessitated modifying the existing Size Effect which was mainly confined to the strength parameter only. Use of high-speed photography enabled the detection of several modes of failure experienced by concrete cylinders subjected to axial impact. v TABLE OF CONTENTS LIST OF FIGURES .
International Journal of Solids and Structures, 2018
The Double Cantilever Beam (DCB) Mode I fracture testing has been widely used in fracture testing... more The Double Cantilever Beam (DCB) Mode I fracture testing has been widely used in fracture testing of especially fiber reinforced polymer composites and adhesive joints. Application of classical DCB testing to plain concrete or
The universal size effect law of concrete is a law that describes the dependence of nominal stren... more The universal size effect law of concrete is a law that describes the dependence of nominal strength of specimens or structure on both its size and the crack (or notch) length, over the entire of interest, and exhibits the correct small and large size asymptotic properties as required. The main difficulty has been the transition of crack length from 0, in which case the size effect mode is Type 1, to deep cracks (or notches), in which case the size effect mode is Type 2 and fundamentally different from Type 1. The current study is based on recently obtained comprehensive fracture test data from three-point bending beams tested under identical conditions. In this test, the experimental program consisted of 80 three-point bend beams with 4 different depths 40, 93, 215 and 500mm, corresponding to a size range of 1:12.5. Five different relative notch lengths, a/D = 0, 0.02, 0.075, 0.15, 0.30 were cut into the beams. A total of 20 different geometries (family of beams) were tested. The p...
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